Hmmm... you can tint GW's Mithril Silver with blue but you have to be very careful or too much blue will get rid of the metal flake. I like to mix Testors Clear blue/red/green in with Mithril silver to get a real nice solid-metallic tint. However if you can't get testors you're kinda stuck there. For the shiny metallic colors use a clear color over top of silver.

I suggest getting someone to ship you a lot of Folk Art metallics, they're like $2US each and work well. They're not going to give you a chromed effect but they do reflect enough light to make them look like metal.

This may help. I bought a gold colored paint (mine was testors but it may not have to be) and I noticed that if I didn't sake the paint up before I used it I got a very watery clear metallic color (I the top of the Can the paste like paint wa sitting at the bottom) that I could mix with other paints, it also worked with silver. It may work with all paints I don't know.